Mirror cracking material

One of the option on Orkut for describing your looks is "mirror cracking material". I always wondered if it's extreme on positive side or negative? Is one too beautiful that mirror cracks in ecstasy or too ugly (for lack of better word) that mirror cracks in disgust? When I saw the order of options, it turns out that real meaning is later. Of course, what appears to me is that choosing this option allows people to mockingly hide their real disposition. You know, like, when you say 'I am stupid', you can be sure that people will think of you anything but stupid. What stumps me next is the necessity to both mention and hide, rather than just not mention, since answering question on look is after all voluntary. Is it attempt at being funny and/or casual?

We are, of course, assuming that one really is not that ugly. Which even if one is, one will never mention by oneself, as corroborated by absence of any profile with "large" build (body type). Interestingly "mirror cracking" beauty is funny but "large" body is not. Difference, I think, lies in the word used. If it were to be "ugly" then it will be as unfunny as "large", it's just too painful to self-describe like this, and others may trust what you say since meaning is clear. On the other hand, "mirror cracking" cannot ever literally be true, so even when it implies lower order of beauty, it is funny. If "you can sit on me" were to replace "large", I guess one will see more usage.